Harry Potter and the Half-Blood Prince - J.K. Rowling

J.K. Rowling
HARRY POTTER AND THE HALF-BLOOD PRINCE
“Where?” asked Harry. “How?”
“You handed it to me, Harry,” said Dumbledore. “The diary, Riddle’s
diary, the one giving instructions on how to reopen the Chamber of Secrets.”
“I don’t understand, sir,” said Harry.
“Well, although I did not see the Riddle who came out of the diary, what
you described to me was a phenomenon I had never witnessed. A mere memory
starting to act and think for itself? A mere memory, sapping the life
out of the girl into whose hands it had fallen? No, something much more
sinister had lived inside that book... a fragment of soul, I was almost sure of
it. The diary had been a Horcrux. But this raised as many questions as it
answered.
“What intrigued and alarmed me most was that that diary had been intended
as a weapon as much as a safeguard.”
“I still don’t understand,” said Harry.
“Well, it worked as a Horcrux is supposed to work — in other words, the
fragment of soul concealed inside it was kept safe and had undoubtedly
played its part in preventing the death of its owner. But there could be no
doubt that Riddle really wanted that diary read, wanted the piece of his soul
to inhabit or possess somebody else, so that Slytherin’s monster would be
unleashed again.”
“Well, he didn’t want his hard work to be wasted,” said Harry. “He wanted
people to know he was Slytherin’s heir, because he couldn’t take credit
at the time.”
“Quite correct,” said Dumbledore, nodding. “But don’t you see, Harry,
that if he intended the diary to be passed to, or planted on, some future Hogwarts
student, he was being remarkably blasé about that precious fragment
of his soul concealed within it. The point of a Horcrux is, as Professor Slughorn
explained, to keep part of the self hidden and safe, not to fling it into
somebody else’s path and run the risk that they might destroy it — as indeed
happened: That particular fragment of soul is no more; you saw to that.
“The careless way in which Voldemort regarded this Horcrux seemed
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